Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Subordinated Borrowing [Line Items]
Federal tax credits recognized in tax expense	$ 800	$ 660
Investment tax credits	5,070	$ 17,490
Investment carrying amount	8,667,837		$ 8,727,958
Unfunded capital and other commitments	7,586,288		7,659,695
Maximum exposure to loss, unconsolidated VIEs	66,560		59,649
Variable Interest Entity [Line Items]
Investment carrying amount	8,667,837		8,727,958
Variable interest entity, primary beneficiary
Subordinated Borrowing [Line Items]
Investment carrying amount	79,540		87,370
Unfunded capital and other commitments	0		0
Variable Interest Entity [Line Items]
Investment carrying amount	79,540		87,370
Variable interest entity, not primary beneficiary
Subordinated Borrowing [Line Items]
Investment carrying amount	76,374		79,228
Unfunded capital and other commitments	71,407		80,719
Variable Interest Entity [Line Items]
Investment carrying amount	$ 76,374		$ 79,228